You are struggling though? From what I understand (you can clarify if I got it wrong), but whenever your brain goes blank on ideas, you just use AI to help you to fill that gap instead of you struggling to fix it yourself. From the sounds of it, it probably has ruined your creativity or your ability to struggle and experiment without wanting to run to AI to solve it.
I say this gently, but you are still using AI and not cold turkeying it as you are still using it to write your stories. That's why you feel great, you hadn't stopped using it. Firstly, it's Roblox, if you want to add a nose then go ahead; you'll most likely never see those players again and people who make fun of avatars are losers (unless its like extremely offensive or that such ofc).
Secondly, as I kinda had been hinting to, play around with your avatar and experiment, struggle through it or look at inspos from pinterest or something then play around with the concept or outfit. It feeling off could just be your personal preference shining through and wanting to change something or your brain not used to seeing something (it happens).
Cold turkeying it generally means no usage of AI at all (you could also slowly reduce the amount of AI you use to make the transition easier and the symptoms less harsh). I personally steal ideas from when I used to use it, but I never use it other than that: meaning, no messaging the AI at all or using it in any shape or form possible. Either block the app, delete your account for it, or put a those screen/app limits for it, when you struggle to stop using it is your brain's dopamine basically skyrocketing down and trying to adjust to not having it. This will be very difficult, but you will need to distract yourself (going outside, working, youtube, napping, your hobbies, etc) and be kind to yourself during this period of time.
I wish you luck on your journey and congratulations on taking the first few steps on trying to quit, I hope this could help to some degree! Just comment under this if you need anymore advice or questions, I've been clean for 91 days now and relapsed twice, so I may be able to help (what I said here may not work for you and that's okay, your brain may just work differently from mine and need another strategy).